For the purposes of this invention the term "sorptive minerals" is defined as clays, distomatious earth, fuller's earth and bentonite that are low in bulk density usually less than 45 lbs./cu. ft., and have the ability to absorb liquids into their pores. Sorptive materials usually contain more than one component but most often have a high percentage of attapulgite, or montmorillonite, or sepiolite, or diatomite. Generally a sorptive mineral that has any of the above as the major component is very likely to have lesser amounts of one or all of the others. Any of the other known clay minerals, such as Kaolinite and illite are commonly present and nonclay minerals and/or silicous materials that cannot be classified as diatomaceous earth may be present. Typical of the latter is silica sand, limestone, iron oxide and gypsum.
Sorptive minerals, which are used as industrial absorbents, soil conditioners, decorative mulch herbicides, insecticide carriers, cat box absorbent and sanitary absorbents for such things as vomit, are generally mined, dried and/or calcined, crushed and screened to a particle size, which depends on the particular use to which it will be applied. This crushing and screening inevitably leads to a waste products known as "fines," which for the purpose of this invention can be defined as a range of particles less than 50 mesh in size. While the "fines" from some specially selected and/or further processed sorptive minerals can be used, for instance, attapulgite as drilling mud, it is generally accepted within the industry that sorptive minerals which are best suited as an absorbent or for decorative purposes and which grade down from 50 mesh have little market demand. In some products, depending on desired final particle size "fines" can be generated in an amount equal to 10% to 60% of the final merchantable product and for some products such as 16/30, 30/60 and 24/48 insecticide grades the "fines" lost will be on the high side of the above range. Obviously, if these "fines" cannot be used they represent an economic loss to the manufacturer and in fact create a disposal problem.
Various methods have been advanced for pelletizing "fines" which generally involve processing the "fines" by compressing them into pellets of a useable size. These methods have proven satisfactory for pelletizing plastic, nonabsorbent clay "fines." Processes for pelletizing sorptive mineral "fines" which use collodial clay as a binder by agglomeration have also been advanced but for the most part have been unsatisfactory because it is difficult to control the pellet size and strength and the resulting pellets are unstable under certain environmental conditions and lack the qualities of the sorptive mineral.